Crane drive system



Sept 5, l944 w. s. BURDlcK ETAL CRANE DRIVE SYSTEM Original Filed Oct. 25, 1941 4 Sheets-Sheet l ATTORNEY vSept 5, 1944- w. s. BuDlcK ETAL 2,357,517

CRANE DRIVE SYSTEM Original Filed Oct. 25. 1941 4 Sheets-Sheet 2 INVENTORS W u WT; BY

xMHIIV. @..MMJIHHINIINIMIEMMwww ATTORNEY Sept 5,1944 w. s. BURDlcK ETAL 2,357,517

CRANE DRIVE SYSTEM Original Filed Oct. 25, 1941 4 Sheets-Sheet 3 fm1 5"Y Q i WHHH HH HH HH www ATTORNEY Sept. 5, 1944. w. s, BuRDlcK :aT/1u.A

CRANE DRYIVVE SYSTEM Original Filed Oct. 25, 1941 4 Sheets-Sheet 4 FIG. 5.

INVENTOR @mj/.f

ATTORNEY Patented Sept. 5, 1944 CRANE DRIVE SYSTEM Will S. Burdick, West Allis, and Henry S. J acobs, Milwaukee, Wis., assignors to Harnischfeger Corporation, Milwaukee, Wis., a corporation of Wisconsin Original application October 25, 1941, Serial No.

416,596. Divided and this application November 4, 1943, Serial No. 508,994

6 Claims.

This invention relates to excavator cranes and the like and to drive systems therefor and resides more particularly in a combination of a continuously running prime mover with power transmission apparatus for such cranes by which the power of the prime mover is applied to effect working functions of such crane by means including a controllable torque transmitter which is dependent for its torque transmitting properties upon the reaction forces of eddy currents induced by controllable magnetic ux concentrations which are forced by the prime mover to traverse a conducting body.

Cranes and excavating cranes employing continuously running prime movers, such as internal combustion engines, are in wide use. Because of the power characteristics of such prime movers, the several instrumentalities to be driven in such cranes are customarily accelerated and driven by friction clutches. This permits the prime mover to continue running at fairly constant rate and at a rate at which power output and torque are fairly high. The speed of the prime mover in such cases is regulated by a governor.

While friction clutches are suliiciently effective for the above purposes to give to such machinery a high degree of utility, several distinctly disadvantageous properties are inherent in the friction clutch. One disadvantage is the continual wear of the friction linings. This necessitates frequent adjustment and periodic replacement of the friction bands or shoes. Another disadvantage is the considerable amount of eiort required to actuate such clutches. To overcome the latter diniculty, self-energizing clutches or servo actuators have been employed, but this gives rise to grabbing, touchiness in response, and a necessity for even more frequent adjustment. Another disadvantage of such -friction clutches is that the speed at which they operate must be limited to avoid the effects of centrifugal force, which would interfere with proper functioning of the parts. In order to obtain suflicient capacity at such lower speeds, such clutches must be made very large and heavy.

Even in the case of friction clutches of good design the operator must possess a high degree of skill in order to obtain high output without damage to the crane. For example, in a crane of substantial size, fitted with a long boom a too sudden engagement of a swinging clutch may easily result in crumpling of the boom. The operator is consequently under a constant mental strain in choosing the proper compromise between high output and disaster.

Even when disastrous grabbing is avoided and normal slipping engagement is preserved, the forces frictionally transmitted by friction clutches rise to a peak with great suddenness. This is particularly true of the swing clutches, which are depended upon not only to accelerate all of the swinging parts of the crane, but also to decelerate them and to reverse their direction of rotation. In other words, said clutches are normally used to a considerable extent as brakes under conditions where the rate of slip amounts to 200% of full driving speed. The peak torque demand placed upon the prime mover by this arrangement is suiiiciently severe to markedly slow down the running speed of the prime mover and to do so in a very short time interval. The action is so fast that the prime Vmover governor cannot respond in time to offset the deceleration. The characteristics of the internal cornbustion engine are such that power output ability falls off with loss of speed. By the time the governor comes into play the prime mover is no longer in condition to meet the load imposed. The power output of the engine is so impaired by the action that the swinging functions of the crane are rendered sluggish. This impairment of the power source also adversely affects the rate at which hoisting or other functions can be carried on simultaneously with swinging. While this adverse property of the arrangement may be alleviated in part by skillful manipulation on the part of the operator, it cannot be eliminated.

Among the objects of this invention are: the elimination of frictionally engaging parts, with consequent avoidance of the frequent adjustment and replacement of friction members; the reduction of operator elfort to the mere throwing of a switch; the elimination of all possibility of grabbing, with consequent elimination of the hazard attendant thereon; the limitation of peak torque demands so as to provide sufficient time for the prime move;1 governor to eiectively meet altering conditions and thus to increase the overall work capacity of the crane and the eliminatio-n of racking shocks and forces which produce unduly rapid deterioration of the machine. These and other objects of this invention and the means by which the same are accomplished will become apparent from the' description of the invention which follows. This invention is herein described by reference to the accompanying drawings which form a part hereof and in which there is set forth by way of illustration Yposite each of the pole pieces 24,

AI9, as shown. The :dns

-shaft I to turn therewith is -passes therethrough from and not of limitation one form of the apparatus of this invention.

In the drawings:

Fig. 1 is a side elevation, with parts broken away, of a crane embodying one form of the apparatus of this invention;

Fig. 2 is a plan view of the apparatus shown in Fig. 1;

Fig. .3 is a fragmentary detailed end elevation, partly in section, of the eddy current coupling means viewed as indicated by the broken lines 3-3 in Figs. 2 and 4;

Fig. 4 is a detailed side elevation, with parts broken away, of the eddy current coupling means; and

Fig. 5 is a wiring diagram of the electrical circuit employed in the apparatus of this invention.

Referring now to the drawings, there is shown in Fig. 1 a cab I mounted for rotation upon a crawler base 2. A fragment of a boom 3 is shown mounted in conventional manner on the forward end of the cab. .A prime mover in the form of an internal combustion engine 4 is located at the rear of the cab I, as shown. The prime mover 4 is of the continuously running type, regulated by a governor 5 which controls the throttle 6. Power from the prime mover 4 is delivered through gearing 1, 8 and 9 to the jack-shaft I0. The jack shaft I0 serves todeliver through continuously running gear II and I2 power for the operation of drum-shaft I3. Jack-shaft IU also extends across the cab I through the magnetic coupling means I4 and I5, which serve to deliver power or causing swinging motion of the crane.

In the form of the apparatus shown and herein described, the instrumentalities mounted upon the drum-shaft I3 for performing the various hoisting functions of the crane are arranged to be frictionally driven in the conventioual manner and the details thereof are therefore not described. Ihe magnetic coupling means I4 and I5,'however, employed to regulate the swinging lmotion of the crane, are of novel form not here- Vrim I1 is provided with a peripheral groove 25 in vwhich there is accommodated a pair of peripheral magnetic windings 2|. The outer periphery of the rim I1 is slotted transversely -by alternate Ydeep and shallow slots 22 and 23 forming a plurality ofroutwardly extending pole pieces 24 which extend' outwardly along the sides of the coils 2I,

the pole pieces 24 being forked at their outer ends the slots 23 positioned therein. Op-

standing to the left in Fig. 3, are located integrally-formed radial ns 25, which extend inwardly toward the hub 25 serve to enhance the rate of flow o air through the apparatus.

Also radially held with respect to the jackthe insulating disk 25. The disk 25 is held securely in place between the sleeves 21 and 28, as shown. Mounted upon the opposite sides of the insulating disk 26 are slip-rings 29 and 30, the same being held in place by through-bolts 33. An insulated bushing 34 serves to insulate the through-bolt 33 which the slip-ring 3l] and, in

by reason of like manner, the insulating bushing. 35 serves to insulate the through-bolt which passes therethrough from the slip-ring 29.

The inner ends of the coils 2I are brought through leads and terminals into electrical connection with slip-ring 29, while the outer ends of the coils 2| are brought by leads and terminals 31 into electrical connection with slip-ring 39. The two parts of the pair of coils 2I are thus placed in shunt connection with one another. It is obvious that the windings may consist of a single coil or several coils, as may be desired or convenient. In-the present instance two coils have been shown to permit reconnection for two diierent exciter voltage ranges, purely as a matter of convenience.

Secured to the left-hand face of the rim I1, as viewed in Fig, 3, by means of the bolts 38, is a side nger plate 39. The periphery of the side linger plate 39 is slotted by alternate deep and shallow slots 40 and 4I, respectively, to form the forked pole fingers 42, as shown.

Mounted to turn upon the jack-shaft I0 is a driven coupling member 43, which is held in place for free turning movement upon the roller-bearing 44. The bearing 44 is of the conical thrust type so that the driven member 43 is held positively against endwise displacement with respect to the shaft I0. The driven member 43 comprises the mounting disk 45 to which the cylindrical sleeve 46 is secured by bolts 41, as shown. The internal diameter of the cylindrical sleeve 46 is very slightly largerV than the diameter of the path swept by the outer tips of the pole pieces 24 so that a very small air-gap extends between the sleeve 46 and the ends of the pole pieces 24.

In the drawings this air-gap is shown slightly exaggerated for the purpose of clarity. The sleeve 46, furthermore, extends axially from the mounting disk 45 to a position where it is closely adjacent to the inside faces of the side fingers 42 so that there is a small air-gap Ibetween said ngers and said sleeve extensions. Here again this airgap is shown slightly exaggerated for the sake of clarity.

Keyed to the mounting plate 45 of the driven member 43 is the bevel-pinion 48, which is contained within the reverse gear casing 49. The pinion 48 is positioned to mesh with a driven bevel-pinion 59 secured to the end of vertical shaft 5I, which extends downwardly, as shown, from the gear casing 49.

The magnetic coupling means I4 mounted upon the opposite end of jack-shaft I0 is symmetrically similar in all respects to the magnetic coupling means I5, the same being provided with a driving member 52 and a driven member 53, which is rigidly associated with bevel-pinion 54.

In order to supply current to the windings 2l, slip ring brushes are positioned to engage the sliprings 29 and 39. One of these is shown in dotted form and designated by the numeral 55 in Fig, 4. When the windings 2I are excited by current supplied thereto through the slip-rings and brushes, as described, a strong magnetic eld is established, following the course of the broken line 56. The flux of this field bridges the gap between the ends of slotted pole pieces 24 and the cylindrical sleeve 46 extending through the cylindrical sleeve, as shown. When the driving portion I6 is rotated and the cylindrical sleeve 45 is stationary or lags react against the movement of the localized flux zones through the material of the sleeve 46. As a result, torque is transmitted from the driving member I6 to the driven member 43, this torque being a function of the intensity of flux and the rate of slip between the driving and driven member. The power disappearance represented by the torque and rate of slip appears largely in the form of resistance heat within the conducting sleeve 46. The heat thus created causes the temperature of sleeve 46 to rise until the rate of heat dissipation therefrom equals the rate at which such heat is being generated. The draft of air caused by the configuration of the driving member I6 and the ns 25 facilitates this heat dissi- 1,

creasing the air gap between it and the pole pieces 24. This same expansion, however, tends to reduce the air gap between the sleeve 46 and the side fingers 42. A flux path thus becomes established, as indicated by the broken line 51, which` flux path has a reluctance not greatly differing from that of path 56. In this way thermal expansion effects are compensated for in such a way that operating characteristics remain substantially constant regardless of operating temperatures.

As appears more clearly in Fig. l, the vertical shaft I carries a pinion 58 which is in mesh with idler gear-.59. The gear 59 meshes with gear 6D, mounted to be connected by dog-clutch 6I with a swing pinion shaft 62. Mounted upon the lower end of the shaft 62 is a swing pinion 63 which meshes with internal ring gear 64, which is securely held upon the crawler base 2. The ring gear 64 is surrounded by a roller track 65 also secured to the crawler base 2 and interposed between the track 65 and the cab I is a race of rollers 66. A central guiding gudgeon, concentric with the roller track 5, is employed in conventional manner, but not shown, and in this way the cab I is mounted for swinging movement upon the crawler base 2. Swinging movement is brought about by driving the pinion 63, which is accomplished when desired by engaging the dogclutch 6I and by energizing the windings of drive members I6 or 52.

In order to place the control of the swinging functions of the apparatus within reach of the operator, a switch 61 of the single pole, double throw type is locatedat the operators station. The center tap of switch 61 is connected as shown in Fig. 5 by lead 68 with one terminal of generator 69. One of the selectable taps 61 is connected by lead 10 with one of the slip-rings which is in connection with winding 2I. The other selectable tap of the switch 61 is connected by the lead 1I with a slip-ring which is in connection with a winding 12 contained within the driving member 52 but shown diagrammatica-lly only in Fig. 5. The other terminal of the generator 69 is permanently connected, as shown, with the slip-rings which are in connection with the upper ends of the windings 2I and 12. The operator may thus, by manipulation of the switch 61, energize either of the magnetic-coupling means I4 or I5 at will to produce either right-hand or left-hand swinging of the cabl.

The generator 69 is preferably of the type having a shunt field winding 13 having in series therewith a variable resistance 'I4 positioned at the operators location so that it may be regulated at will.

A generator of this type has, as a typical characteristic, high open circuit voltage and a tendency for its voltage to drop as load -is applied. A generator of this type is preferably availed of in the apparatus of this invention for the reason that the windings 2I and 12 are of high impedance and if normal operating voltage is applied thereto a considerable time elapses before full operating current becomes established. By use of the shunt type generator such as generator 69, howevery application of high initial voltage of the generator to the windings 2| and 12 causes a rapid building up of current and a very prompt response on the part of the magnetic coupling means I4 and I5. By the time operating current is built up to normal operating levels the output voltage of generator 63 has fallen to normal operating levels and thus there is no condition under which excessive current is able to flow in any part of the circuit.

In order that the generator 69 exhibit the characteristics desired, it is necessary that it be driven at a fairly constant rate and for this reason it is preferred that generator 69 be mounted as shown in Fig. 2 and directly driven by the prime mover 4.

Because of the large moment of inertia of the cab I and associated parts, including the boom 3, the swinging function is one-accomplished largely under conditions 0f slip between the prime mover and the swinging cab. During substantially the entire swinging movement acceleration or deceleration is taking place. Therefore, in a machine in which a continuously running prime mover is employed, means which admit of slip must be employed. The magnetic coupling means of this invention admit of this slip without producing frictional wear and at the same time such slip is available for transmission of the torque required. The latter factor is of primary importa-nce, since the torque transmittable by electromagnetic coupling means is greatest when the slip is greatest and falls olf accordingly as slip -is reduced. The electromagnetic coupling means of this invention are therefore capable of transmitting maximum torque at such times when maximum torque is desired, that is, when acceleration at the outset of the swing is required and when deceleration and reversal of direction of swing are required.

The peak torque demand which the apparatus of this invention places upon the prime mover may be adjusted and fixed at any quantity desired by adjustment of the rheostat 14, or by initial selection of appropriate circuit constants. It is thus beyond the power of the operator, once the system is adjusted, to impose upon the prime mover more than a predetermined peak torque demand. This predetermined peak torque demand may be easily adjusted to a maximum at which the prime mover will continue to run at a reasonably constant rate of speed within the capacity of the governor to maintain satisfactory control. In this way the full power output of the engine is not impaired and the apparatus as a whole is protected against disastrous acceleration, such as might cause crumpling of the boom. While initial high acceleration is thus precluded, sustained accelerations are nevertheless procured to an extent heretofore unattainable in drive systems employing friction clutches. Furthermore, arrangement of the generator which furnishes exciter current to be driven by, or in proportion to, the speed of the prime mover, causes a load-governing action to take place. The output voltage of the generator being thus driven will fall olf with any falling off in speed of the engine. Thus, if the operator so operates the machine as to cause the engine to lose speed in spite of the action of the governor, excitation voltage and current will fall oif and the load transmittable by the clutches will diminish. This automatic dropping of the load thus safeguards against serious killing of the engine, even though the operator has adjusted excitation current to avail of the very limit of the power output of the prime mover. As a result, working cycles may be completed with greater dispatch and full power of the engine is made available for the carrying on of simultaneous functions, such as hoisting during swinging, and the like. The operator is relieved of the mental strain of attempting to avoid injurious and damaging shocks and is encouraged to press his operations toward maximum output. This makes possible a substantial overall increase in the work capacity of the crane so that a substantially smaller crane is capable of performing the work which has heretofore required a crane of substantially greater bulk, weight, and expense.

While this invention has been herein described in connection with a drive system adapted for producing the swinging movement of the crane, the other operating functions of the crane may be similarly driven and controlled, if desired.

Because of the high degree of slip normally existing in the swinging driving system, however, electro-magnetic coupling means are of particular value.

While this invention has been herein described by reference to a specific instance of denite application and use, it is intended that the protection of Letters Patent to be granted hereon be not unnecessarily limited thereby, but that such protection extend to the full limit of the inventive advance disclosed herein as defined by the claims hereto appended.

This case is a division of our co-pending case, Serial No. 416,596, led October 25, 1941, for Crane drive system.

We claim:

l. In a self-powered cab and base of the type employed in hoisting and digging cranes, the combination comprising a base upon which said cab is rotatably mounted, a prime mover mounted on said cab, power transmission means between said prime mover and said base adapted to apply the power of said prime mover to cause said cab to rotate on said base, said power transmission means including a pole piece member, an eddy current member, said pole piece member being provided with a peripheral groove, windings positioned in said peripheral groove, a plurality of pole pieces ranged along the sides of said peripheral groove and spaced from one another, the ends of said pole pieces being positic-ned to lie within a surface of revolution coaxial with the axis of said pole piece member, said eddy current member being positioned in close proximity to the path swept by the ends of said pole pieces and being composed of electrically conductive magnetic material, and supplementary pole ngers having faces positioned to lie in a surface of revolution extending laterally with respect to the surface swept by the ends of said pole pieces, said supplementary lingers being secured to said pole piece member in close proximity to said eddy current member.

2. In. a power transmission suitable for controlling the swinging movements of a crane having a cab rotatably. mounted cna base, the combination comprising a prime mover mounted on said cab, a jack-shaft mounted on said cab drivably connected to said prime mover, a pair of eddy-current-clutch driving members, each having windings for exciting the same secured to said jack-shaft to rotate therewith, an eddycurrent clutch driven member cooperatively positioned with respect to each of said driving members and adapted to be driven separately thereby whenthe windings thereof are separately energized, a bevel pinion secured to each of' said driven members, a driven bevel gear in meshing relationship with both of said bevel pinions, said bevel gear being adapted to be driven in one direction when one of said driven clutch members is driven by energization of the winding of the corresponding clutch driving member and adapted to be driven in the opposite direction when the other of said driven lclutch members is ldriven by energization of the winding of its corresponding clutch driving inember, gearing connecting said bevel gear with said base adapted to cause said cab to swing when said bevel gear is driven, and means controllable by an operator for separately energizing the windings of said eddy-current-clutch driving members.

3. In a power transmission suitable for controlling the swinging movements of a crane having a cab rotatably mounted on a base, the combination comprising a prime mover mounted on said cab, a jack-shaft mounted on said cab driveably connected to said prime mover, a pair of eddy-current-clutch-driving members each having windings for exciting the same secured to said jack-shaft to rotate therewith, an eddy-current clutch-driven member cooperatively positioned with respect to each of said driving members and adapted to be driven separately thereby when the windings thereof are separately energized, a bevel pinion secured to each of said driven members, a driven bevel gear in meshing relationship with both of said bevel pinions, said bevel gear being adapted to be driven in one direction when one of said driven clutch members is driven by energization of the winding of the corresponding clutch-driving member and adapted to be driven in the opposite direction when the other of said driven clutch members is driven by cnergization of the winding of its corresponding clutch-driving member, gearing connecting said bevel gear with said base adapted to cause said cab to swing when said bevel gear is driven, and means controllable by an operator adapted to alternatively energize the windings of said eddy-current clutch-driving members.

4. In a power transmission suitable for controlling the swinging movements of a crane having' a cab rotatably mounted on a base, the combination comprising a prime mover mounted on said cab, a jack-shaft mounted on said cab drivef ably connected to said prime mover, a pair of eddy-current clutch-driving members comprising peripherally grooved magnetic bodies with radially extending spaced pole pieces ranged on both sides of said groove, said pole pieces having faces disposed within a 'cylindrical surface, magnetic windings in the grooves of said driving members, a cylindrical sleevelike eddy-current clutch-driven member surrounding each of said driving members, said driven members being coaxially disposed with respect to saidl jack-shaft and mounted for rotation thereon, al bevel pinion secured to each of said driven members, a driven bevel gear in meshing relationship with both of said bevel pinions, said bevel gear being adapted to be driven in one direction when one of said driven clutch members is driven by energization of the winding of the corresponding clutchdriving member and adapted to be driven in the opposite direction when the other of said driven clutch members is driven by energization of the winding of its corresponding clutch-driving member, gearing connecting said bevel gear with said base adapted to cause said cab to swing when said bevel gear is driven, and means controllable by an operator for separately energizing the windings of said eddy-current clutchdriving members.

5, In a power transmission suitable for controlling the swinging movements of a crane having a cab rotatably mounted on a base, the combination comprising an internal combustion engine having a governor mounted on said cab, a jack-shaft mounted on said cab driveably connected to said prime mover, a pair of eddycurrent clutch-driving members each having windings for exciting the same secured to said jack-shaft to rotate therewith, an eddy-current clutch-driven member cooperatively positioned with respect to each of said driving members and adapted to be driven separately thereby when the windings thereof are separately energized, a bevel pinion secured to each of said driven members, a driven bevel gear in meshing relationship with both of said bevel pinions, said bevel gear being adapted to be driven in one direction when one of said driven clutch members is driven by energization of the winding of the corresponding clutch-driving member and adapted to be driven in the opposite direction when the other of said driven clutch members is driven by energization of the winding of its corresponding clutch-driving member, gearing connecting said bevel gear with said base adapted to cause said cab to swing when said bevel gear is driven, a generator having a shunt field winding mounted to be driven by said prime mover, and a switch controllable by an operator adapted to connect said generator to either of the windings of said eddy-current clutch-driving members but not to both simultaneously.

6. In a power transmission suitable for controlling the swinging movements of a crane having a cab rotatably mounted on a base, the combination comprising a prime mover mounted on said cab, two eddy-current-clutch driving niembers rotatably mounted on said cab and adapted to be driven by said prime mover, an eddy-current-clutch driven member cooperatively positioned with respect to each of said driving members to form two pairs of driving and driven members, a winding for each pair of driving and driven clutch members associated therewith in position to establish when energized a magnetic field mutual to the driving and driven members of each pair, a gear train mounted on said cab in engagement with means mounted on said base and adapted to cause said cab to swing when said train is driven, a gear meshing with said train and adapted to be driven by one of said driven clutch members for driving said train in one direction, and a second gear meshing with said train and adapted to be driven by the other driven clutch member for driving said train in the opposite direction, and means controllable by an operator for separately energizing said windings.

WlLL S. BURDICK. HENRY S. JACOBS, 

